Wow heroes has a simple little hit calculator. You can find it here.
We should all know how to calculate warlock hit rating.This confirms it and gives a quick check of raid buffs you should look out for to increase your hit rating.
My Rogue is constantly jabbering on about hit rating. As a melee class they have a hit cap for their specials and then for their white damage. When designing your gear you have to decide early what your goals are for hit.
It is very easy to use. I looked at the information on warlocks, hunters, and rogues so the data should be good for all classes. If your perception of hit is different from the tool check if you can back calculate what they are doing. Sometimes you can find things you are missing that way.